1. Field of the Invention
The present invention relates to an eye image pickup device for obtaining an image of an eye of a human being.
2. Description of the Related Art
Iris images are employed for management of room accesses of entrances/exits, or for verifying the identities of users of ATMs (Automated-Teller Machines), computers or cellular phones. Because human iris patterns, which are established during infancy, are distinctive and vary from person to person, even between the right and left eyes of any specific individual, the use of iris pattern data is exceptionally effective when employed for personal identification.
A well-known eye image pickup device for reading iris patterns uses a camera with a wide field of view to identify the position of an eye, and obtains eye images by adjusting the field of view of the camera equipped with a telephoto lens (for example, JP-A-10-137225). However, the structure of this device is too large, and can not be employed for a portable device, such as a cellular phone.
An eye image optical pickup device shown in FIG. 9 is also well-known. This optical pickup device includes an object lens 1 and a pickup element 2, such as a CCD, and a half mirror or a cold mirror 21 that is disposed in front of the object lens 1. The cold mirror 21 reflects visible light, but does not interfere with the passage of infrared light. Thus, the cold mirror 21 can be used for image pickup when infrared illumination is employed. When a person""s eye is positioned along a light axis 5 of the optical pickup device, the eye is reflected by a specific portion of the mirror 21 and a precise image can be obtained by the device in FIG. 9. However, since the mirror 21 required for this device is larger than the object lens 1, mounting such a mirror 21 on a portable device would be difficult. Further, when the eye of a person is not reflected by the mirror 21 as shown in FIG. 9, it is difficult for the person to determine in which direction to move to position the eye correctly.
Another eye image pickup device, for obtaining an iris pattern, has been proposed wherein first and second edge means, provided within the field of view of a camera with a telephoto lens, make it possible for a user to adjust eye positioning (see JP-W-10-505180, for example). However, since the first and second edge means are disposed forward of the object lens of the camera, the structure size is increased, and the pickup device can not appropriately be applied for a portable device, such as a cellular phone.
To resolve the shortcomings of the conventional art, it is an objective of the present invention to provide a simply structured eye image pickup device that can be mounted in a variety of devices, specifically including portable devices, and that can obtain precise eye images.
To achieve the above objective, according to one aspect of the invention, an eye image pickup device includes: a marker provided coaxially along a light axis of an optical pickup system for obtaining the eye image; and a light guide unit for guiding visible light, emitted by a visible light source, on the route of a pickup light path to the object lens, wherein the light guide unit is located nearer the image pickup unit than the marker, and a center of the light guide unit is coincident with the light axis so that the person can see both the light guide unit and the marker. Owing to this, because of the positional relationship existing between the marker and the guided visible light that can be observed through the object lens, one person can determine the precise direction in which to move one""s eye.
Furthermore, the light guide unit is located nearer the image pickup unit than a midpoint between the object lens and the image pickup unit. Owing to this, the light guide unit is not visible to the eye for which no image is to be obtained, and the position of the other eye, for which an image is to be obtained, can be easily adjusted.
Further, the marker is placed on the object lens. Owing to this, the size of the eye image pickup device is not increased.
Furthermore, the marker is constituted by a light shielding portion that shields a part of the pickup light path. Owing to this, the marker can be easily recognized visually.
Further, the light shielding portion is a black sticker that is glued to the object lens, or a black paint that is coated on the object lens.
The light shielding portion may also be a white sticker or a yellow sticker that is glued to the object lens, or a white paint or a yellow paint that is coated on the object lens. When a white paint or the like is used to coat the light shielding portion, the position of the light shielding portion can be more easily identified.
Further, the light shielding portion is provided in a ring shape in a periphery portion of the object lens.
Furthermore, the light shielding portion provided in a ring shape in the periphery portion of the object lens is formed by a lens holder of the object lens. In the case where the light shielding portion is formed by the lens holder, the manufacturing cost will be lowered.
Further, the light guide unit includes an optical fiber cable, one end of which is positioned opposite the visible light source and the other end of which is coaxially arranged with the light axis As a result, the structure of the light guide unit can be simplified.
Furthermore, a mirror is positioned between the object lens of the optical pickup system and the image pickup unit, and the light guide unit includes a visible light transmission portion located on the periphery of the light axis of the mirror. By employing this arrangement, a compact eye image pickup device can be made.
The visible light guided by the light guide unit may be obtained from a two-color LED that is located behind the visible light transmission portion, and the color of the visible light is changed depending on whether or not is the focus is adjusted. By employing this arrangement, at the time of adjusting the focus it is not necessary to watch the monitor screen.
Moreover, the image pickup device further includes: infrared light illumination means; and a visible light shielding filter, wherein an object is illuminated by the illumination means, and wherein the visible light shielding filter is positioned between the image pickup unit and a position to which the visible light is guided, and the visible light shielding filter shields the visible light guided into the image pickup unit. With this arrangement, an eye image can be obtained using infrared light, and any effect which visible light may have on the image pickup element can be removed, thereby ensuring that a high-precise image can be secured.